Upon its release due to cell lysis, bacterial DNA has the ability to stimulate the immune system causing serious damage in tissue. Intraperitoneally injection of P. aeruginosa DNA in rats caused several histopathological changes in the splenic tissue included; a marked germinal center hyperplasia in the white pulp which results in the increase of follicles number within germinal center. Furthermore, apoptotic debris engulfed by macrophages in the marginal zone was noticed. Hemosiderin and degenerated cells were observed as well. In a conclusion, even though the bacterial cells are dead, their remains, especially DNA can cause damage to tissue.